Gas sensor

ABSTRACT

A gas sensor includes a first electrode, a gas detecting layer disposed on the first electrode, and an electric-conduction enhanced electrode unit being electrically connected to the first electrode and the gas detecting layer. The electric-conduction enhanced electrode unit includes an electric-conduction enhancing layer and a second electrode electrically connected to the electric-conduction enhancing layer. The electric-conduction enhancing layer is electrically connected to the gas detecting layer and is made of an electrically conductive organic material.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority of Taiwanese Invention PatentApplication No. 107138044, filed on Oct. 26, 2018.

FIELD

The disclosure relates to a gas sensor, more particularly to a gassensor including an electric-conduction enhanced electrode unit.

BACKGROUND

In recent years, due to increasingly serious air pollution problems, gassensors are becoming more important. A conventional gas sensor withnanostructures has excellent gas sensing properties, and thus has a widerange of applications, from being used in daily life, such as in carbonmonoxide detectors or smoke detectors, to being applied to the detectionof explosive or harmful gases in factories. The operation of theconventional gas sensor is mostly performed through measurement of thechange of the resistance value after its component material reacts withthe gas to be detected.

Even though the conventional gas sensor with multi-layer side walls canaccurately detect the gas to be detected by changing the sensing layermaterial, its sensitivity still needs to be improved as to enhance theefficiency of the gas sensor.

In order to increase the surface area for reaction between the sensingmaterial and the gas to be detected so as to improve the sensingefficiency of the gas sensor, the inventors have previously usedelectrode formed with nanometer micropores which the gas penetrates toreaction with the sensing material. The increased surface area forreaction improved the efficiency of the gas sensor.

In order to produce these electrodes formed with a plurality ofmicropores, first, several nano-spheres are attached to a semi-finishedproduct, then, a metal layer is formed on the semi-finished product in aplating manner, and finally, the nano-spheres are removed so as to getthe final finished product. However, it is not easy to control thestable distribution and attachment of the nanospheres, and unevendistribution of the nanospheres affects the number and distribution ofthe micropores on the subsequently formed electrodes, which may, inturn, affect the sensing results. Thus, mass production of theconventional gas sensors with the microspore is difficult. In addition,the steps of coating and removal of nanospheres significantly lengthensthe manufacturing process, making the conventional gas sensor even lesssuitable for mass production.

SUMMARY

Therefore, the object of the disclosure is to provide a gas sensor thatcan alleviate at least one of the drawbacks of the prior art.

According to a first aspect of the disclosure, a gas sensor includes afirst electrode, a gas detecting layer disposed on the first electrode,an electric-conduction enhanced electrode unit being electricallyconnected to the first electrode and the gas detecting layer, and aninsulating unit. The electric-conduction enhanced electrode unitincludes an electric-conduction enhancing layer and a second electrodeelectrically connected to the electric-conduction enhancing layer. Theelectric-conduction enhancing layer is electrically connected to the gasdetecting layer and is made of an electrically conductive organicmaterial. The insulating unit is disposed on the first electrode forpartially separating the first electrode from the gas detecting layerand the electric-conduction enhanced electrode unit.

According to a second aspect of the disclosure, a gas sensor includes afirst electrode, a gas detecting layer disposed on the first electrode,an electric-conduction enhancing electrode unit electrically connectedto the first electrode and the gas detecting layer.

The electric-conduction enhanced electrode unit includes anelectric-conduction enhancing layer and a second electrode electricallyconnected to the electric-conduction enhancing layer. Theelectric-conduction enhancing layer is electrically connected to the gasdetecting layer and is made of an electrically conductive organicmaterial

The second electrode of the electric-conduction enhanced electrode unitincludes a plurality of spaced-apart electrode portions formed on thegas detecting layer and interposed between the electric-conductionenhancing layer and the gas detecting layer. Any two adjacent ones ofthe electrode portions are formed with a second gap therebetween toexpose the gas detecting layer from the second gap. Theelectric-conduction enhancing layer extends into the second gaps to bein contact with the gas detecting layer.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the disclosure will become apparent inthe following detailed description of the embodiments with reference tothe accompanying drawings, of which:

FIG. 1 is a schematic sectional view of a first embodiment of a gassensor according to the disclosure;

FIG. 2 is a fragmentarily schematic top view illustrating a secondelectrode and an insulating unit of the first embodiment;

FIG. 3 is a fragmentarily schematic sectional view of a variation of thefirst embodiment;

FIG. 4 is a perspective view, illustrating another configuration of theinsulating unit of the first embodiment;

FIG. 5 is a fragmentarily schematic sectional view of another variationof the first embodiment;

FIG. 6 is a fragmentarily schematic sectional view of a secondembodiment of a gas sensor according to the disclosure;

FIG. 7 is a graph of current versus voltage illustrating comparison of adetecting current-applied voltage relationship of Example 1 of the firstembodiment with that of Comparative Example 1;

FIG. 8 is a graph of current versus voltage illustrating comparison of adetecting current-applied voltage relationship of Example 2 of the firstembodiment with that of Comparative Example 2;

FIG. 9 is a graph of current versus voltage illustrating comparison of adetecting current-applied voltage relationship of Example 3 of the firstembodiment with that of Comparative Example 3;

FIG. 10 is a graph of current versus voltage illustrating comparison ofa detecting current-applied voltage relationship of Example 4 of thefirst embodiment with that of Comparative Example 4;

FIG. 11 is a graph of current versus voltage illustrating comparison ofa detecting current-applied voltage relationship of Example 5 of thefirst embodiment with that of Comparative Example 5;

FIG. 12 is a graph of current versus voltage illustrating comparison ofa detecting current-applied voltage relationship of Example 6 of thefirst embodiment with that of Comparative Example 6;

FIG. 13 is a graph of current over time for illustrating ammoniadetection using the gas sensor of Example 4 of the first embodiment;

FIG. 14 is a graph of current over time for illustrating ammoniadetection using the gas sensor of Comparative Example 4;

FIG. 15 is a graph of current over time for illustrating ammoniadetection using the gas sensor of Example 5 of the first embodiment;

FIG. 16 is a graph of current over time for illustrating ammoniadetection using the gas sensor of Comparative Example 5;

FIG. 17 is a graph of current over time for illustrating ammoniadetection using the gas sensor of Example 6 of the first embodiment;

FIG. 18 is a graph of current over time for illustrating ammoniadetection using the gas sensor of Comparative Example 6;

FIG. 19 is a graph of current over time for illustrating ammoniadetection using the gas sensor of Example 1 of the first embodiment;

FIG. 20 is a graph of current over time for illustrating ammoniadetection using the gas sensor of Comparative Example 1;

FIG. 21 is a graph of current over time for illustrating ammoniadetection using the gas sensor of Example 2 of the first embodiment;

FIG. 22 is a graph of current over time for illustrating ammoniadetection using the gas sensor of Comparative Example 2;

FIG. 23 is a graph of current over time for illustrating ammoniadetection using the gas sensor of Example 3 of the first embodiment; and

FIG. 24 is a graph of current over time for illustrating ammoniadetection using the gas sensor of Comparative Example 3.

DETAILED DESCRIPTION

Before the present invention is described in greater detail, it shouldbe noted that where considered appropriate, reference numerals orterminal portions of reference numerals have been repeated among thefigures to indicate corresponding or analogous elements, which mayoptionally have similar characteristics.

Referring to FIGS. 1 and 2, a first embodiment of a gas sensor accordingto the disclosure includes a substrate 2, a gas detecting layer 5, anelectric-conduction enhanced electrode unit 4, and an insulating unit 3.The substrate 2 includes a substrate body 21 and a first electrode 22formed on the substrate body 21. The substrate body 21 serves as asupporting substrate and maybe made of an electrically insulatingmaterial selected from polymers, glass, or ceramic. The first electrode22 may be made of an electrically conductive material selected frommetal, electrically conductive metallic compound or electricallyconductive organic material, for example, gold, aluminum, silver,calcium, zinc oxide, indium tin oxide, molybdenum oxide, lithiumfluoride, etc. In this embodiment, the material of the first electrode22 is exemplified as indium tin oxide (ITO).

The gas detecting layer 5 is disposed on the first electrode 22oppositely of the substrate body 21. The electric-conduction enhancedelectrode unit 4 is electrically connected to the first electrode 22 andthe gas detecting layer 5 and includes an electric-conduction enhancinglayer 42 and a second electrode 41 electrically connected to theelectric-conduction enhancing layer 42. The electric-conductionenhancing layer 42 is electrically connected to the gas detecting layer5 and is made of an electrically conductive organic material.

In alternative embodiments where the first electrode 22 has supportingproperties, the substrate body 21 may be omitted from the substrate 2.

The insulating unit 3 is disposed on the first electrode 22 forpartially separating the first electrode 22 from the gas detecting layer5 and the electric-conduction enhanced electrode unit 4. The insulatingunit 3 includes a plurality of insulating members 31 disposed on thefirst electrode 22. Any two adjacent ones of the insulating members 31are formed with a first gap 32 therebetween so as to expose the firstelectrode 22 from the first gap 32, each of the first gaps 32 beingsurrounded by two corresponding adjacent ones of the insulating members31. In a variation of the first embodiment, the first gaps 32 are inspatial communication with each other (see FIG. 4) to separate theinsulating members 31 from each other. The insulating members 31 maybemade of an electrically insulating material selected frompoly(4-vinylphenol) (abbreviated as PVP) or polymethylmethacrylate(abbreviated as PMMA).

The gas detecting layer 5 disposed on the first electrode 22 is reactivewith a gas to be detected. Upon reaction with the gas to be detected,one or more electrical properties of the gas detecting layer 5 maychange. These changes in the electrical properties may be measured usingthe first and second electrodes 22, 41 electrically connected to the gasdetecting layer 5 so as to determine the presence of the gas to bedetected. In this embodiment, as an example, a change in the electricalcurrent flowing through the gas detecting layer 5, which is caused by achange in electrical resistance of the gas detecting layer 5 uponreaction with the gas to be detected, is measured.

The gas detecting layer 5 may be made of an organic material, aninorganic material, or a composite material of organic and inorganicmaterials. For example, the material for making the gas detecting layer5 may be selected from, but is not limited to, the organic materialincluding benzene dithieno-thiophene[3,4-b] thiophene copolymer such aspoly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]](abbreviated as PTB7),9,9-dioctylfluorene-N-(4-butylphenyl) diphenylamine copolymer such aspoly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-(4,4′-(N-(4-butylphenyl)-diphenylamine](abbreviated as TFB), poly(9,9-dioctylfluorene) (abbreviated as PFO),poly(9,9-dioctylfluorene-alt-benzothiadiazole) (abbreviated as F8BT),poly[4,8-bis(5-(2-ethylhexyl)thiophene-2-yl)-benzo[1,2-b;4,5-b′]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyloxycarbonyl)-3-fluoro-thieno[3,4-b]thiophene-)-2,6-diyl] (abbreviated as PBDTTT-EFT),poly[4,8-bis(5-(2-ethylhexyl)thiophene-2-yl)-benzo[1,2-b;4,5-b′]dithiophene-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thieno[3,4-b]-thiophene-)-2,6-diyl](abbreviated as PBDTTT-CT], and poly(3-hexylthiophene-2,5-diyl)(abbreviated as P3HT), or the inorganic material including carbon,silicon, zinc oxide (ZnO), and tungsten oxide (WO₃), titanium dioxide(TiO₂) and indium gallium oxide (IGZO).

The second electrode 41 includes a connecting portion 411 and aplurality of spaced-apart electrode portions 412 extending from theconnecting portion 411. The second electrode 41 may be made of anelectrically conductive material selected from a metal such as aluminum,gold, silver, nickel, etc, a metallic compound such as indium tin oxide,zinc oxide, molybdenum oxide, lithium fluoride, etc, or an organicmaterial such as poly(3,4-ethylenedioxythiophene) -poly(styrenesulfonate) (PEDOT: PSS). In one form, the second electrode 41 may besingle-layered or multi-layered. Since the electrically conductivematerial that may be used for making the second electrode 41 is wellknown in the art, further details are omitted for the sake of brevity.In this embodiment, the material of the second electrode 42 isexemplified as aluminum.

In this embodiment, the electric-conduction enhancing layer 42 and thegas detecting layer 5 extend into the first gaps 32 so as to beelectrically connected with the first electrode 22 and incompletely fillthe first gaps 32, thereby increasing a gas-sensing area of the gassensor. The electrically conductive organic material for making theelectric-conduction enhancing layer 42 may be selected from the groupconsisting of poly (3,4-ethylenedioxythiophene) (abbreviated as PEDOT),polystyrene sulfonate, polypyrrole (abbreviated as PPY), polythiophene(abbreviated as PT), polyphenylene sulfide (abbreviated as PPS),polyaniline (abbreviated as PANI), polyacetylene (abbreviated as PAC),or poly(p-phenylene vinylene) (abbreviated as PPV), and combinationsthereof.

In this embodiment, the gas detecting layer 5 covers the insulatingmembers 31 and extends into the first gaps 32 to cover the firstelectrode 22 exposed therefrom, and the electric-conduction enhancinglayer 42 covers the gas detecting layer 5. Any two adjacent ones of thespaced-apart electrode portions 412 are formed with a second gap 413therebetween. Each of the spaced-apart electrode portions 412 isdisposed between a corresponding one of the insulating members 31 andthe gas detecting layer 5. Each of the second gaps 413 is in spatialcommunication with a corresponding one of the first gaps 32 such thatthe gas detecting layer 5 and the electric-conduction enhancing layer 42extend into the corresponding first gap 32 through the second gap 413.

The purpose of arranging the electrode portions 412 is to cooperate withthe electric-conduction enhancing layer 42 to conduct a detectingcurrent along with the gas detecting layer 5, and the electrode portions412 may have a number of configurations in actual practice.

In a variation of this embodiment, as shown in FIG. 3, each of theelectrode portions 412 are instead disposed on the electric-conductionenhancing layer 42 and oppositely corresponding in position to acorresponding one of the insulating members 31.

Referring to FIG. 5, in yet another variation of this embodiment, theelectric-conduction enhancing layer 42 covers the insulating members 31and extends into the first gaps 32 to cover the first electrode 22exposed therefrom, and the gas detecting layer 5 covers theelectric-conduction enhancing layer 42. Each of the electrode portions412 is disposed on the gas detecting layer 5 oppositely of the firstelectrode 22 and in a corresponding one of the first gaps 32.

Referring back to FIG. 2, in this embodiment of the disclosure, theelectric-conduction enhancing layer 42 made of the electricallyconductive organic material is arranged in cooperation with formation ofthe second electrode 41 into a grating structure. When a voltage isapplied to the gas sensor, the electric-conduction enhancing layer 42may act as an electrode cooperatively with the second electrode 41. Thisincreases the surface area of the gas detecting layer that current mayflow through, which improves sensitivity of the gas sensor.

Furthermore, since the spaced-apart electrode portions 412 may be formedby film-coating and lithography, the production cost is lowered andprecision of the width of the second gaps 413 among the electrodeportions 412 is improved. Additionally, the simplified production isalso suitable for mass production.

In the following, a preparation example of the first embodiment of thegas sensor is provided. First, the first electrode 22 and the insulatingunit 3 are sequentially formed on the substrate body 21. Then, thespaced-apart electrode portions 412 are respectively formed on theinsulating members 31 using film-coating and lithography. Finally, thegas detecting layer 5 and the electric-conduction enhancing layer 42 arecoated onto the insulating members 31 respectively formed with theelectrode portions 412, extend into the first gaps among the insulatingmembers 31 through the corresponding second gaps 413, and are coatedonto the first electrode 22 exposed from said first gaps 32 to obtainthe gas sensor as shown in FIG. 1.

Since the spaced-apart electrode portions 412 can be formed usingfilm-coating and lithography, the width of the second gaps 413thereamong may be varied depending on designs or sizes of the gas sensoras needed. For example, the width of the second gaps 413 may be between1 micrometer and 1 centimeter. In some embodiments, the width may besmaller than 300 micrometers to keep the electrode portions 412relatively proximal to each other, thereby producing better couplingeffect between the electric-conduction enhancing layer 42 and theelectrode portions 412. Consequently, a higher detecting current isdetectable even when a smaller voltage is applied to the gas sensor. Incertain embodiments, the width is between 1 micrometer and 200micrometers. In certain embodiments, the width is between 5 micrometersand 80 micrometers. In certain embodiments, the width is between 10micrometers and 80 micrometers. In certain embodiments, the width isbetween 5 micrometers and 30 micrometers. In certain embodiments, thewidth is between 10 micrometers and 30 micrometers.

In certain embodiments, the insulating unit 3 may include only one ofthe insulating members 31 in the absence of any first gaps 32, with thegas detecting layer 5 directly covering the insulating member 31 andextending to the surface of the first electrode 22.

Referring to FIG. 6, a second embodiment of the gas sensor according tothe disclosure is illustrated. In this embodiment, the gas sensor issimilar to the gas sensor the first embodiment in including the gasdetecting layer 5, the first and second electrode 22, 41, and theelectric-conduction enhancing layer 42. The first and second electrode22, 41 and the electric-conduction enhancing layer 42 are the same asthe first embodiment and details of the structures and materials thereofare omitted for the sake of brevity. Specifically, in the secondembodiment, the gas detecting layer 5 has opposite first and secondsurfaces 511, 512. The first electrode 22 is disposed on the firstsurface 511 of the gas detecting layer 5. The spaced-apart electrodeportions 412 are formed on the second surface 512 of the gas detectinglayer 5 and interposed between the electric-conduction enhancing layer42 and the gas detecting layer 5. The gas detecting layer 5 is exposedfrom the second gaps 413 and the electric-conduction enhancing layer 42extends into the second gaps 413 to be in contact with the gas detectinglayer 5.

In one form, the gas detecting layer 5 may be composed of an absorbentbase material with supporting properties and a gas detecting materialabsorbed onto the absorbent base material.

In certain embodiments, the absorbent base material is porous.

A preparation example of the second embodiment is provided. First, thegas detecting material is absorbed onto the absorbent base material toform the gas detecting layer 5. Then, respective formation of the firstelectrode 22 on the first surface 511 of the gas detecting layer 5 andformation of the spaced-apart electrode portions 412 on the secondsurface 512 of the gas detecting layer 5 are carried out usingfilm-coating and lithography. Finally, the electric-conduction enhancinglayer 42 is covered over the spaced-apart electrode portions 412 and theportions of the gas detecting layer 5 exposed from the second gaps 413among the electrode portions 412. Examples of the absorbent basematerial may include oil blotting paper, tissue paper, etc, but is notlimited thereto, as long as the material has the supporting propertiesand is available for the gas detecting material to be absorbed thereon.In this embodiment, the absorbent base material is exemplified as oilblotting paper.

Since the gas detecting layer 5 has both supporting properties and isreactive with the gas to be detected, the first and the secondelectrodes 22, 41 maybe formed directed onto the gas detecting layer 5,which further simplifies the production of the gas sensor of thedisclosure.

Referring to FIG. 7, comparison of the detecting current-applied voltagerelationship of the gas sensor of Example 1 of the first embodiment withthat of Comparative example 1 is illustrated. The curves of Groups (I)and (II) respectively represent results of duplicate experiments inwhich the detecting current is measured at an applied voltage range of 0volt to 10 volts using Example 1 and Comparative example 1. The gassensor of Example 1 has the electric-conduction enhancing layer 42 madeof PEDOT, the gas detecting layer 5 made of PTB7, and the second gaps413 of the second electrode 41 with a width of 10 micrometers (μm). Thegas sensor of Comparative example 1 has a structure and a constitutingcomposition similar to that of the Example 1 except for the omission ofthe electric-conduction enhancing layer 42.

FIGS. 8 to 9 respectively illustrate comparison of the detectingcurrent-applied voltage relationship of the gas sensor of Examples 2 and3 of the first embodiment with that of Comparative examples 2 and 3, ina manner similar to FIG. 7. The gas sensors of Examples 2 and 3 have astructure and a constituting composition similar to that of Example 1,but the widths of the second gaps 413 of the second electrodes 41thereof are 20 μm and 80 μm, respectively. Comparative examples 2 and 3have structures and constituting compositions respectively similar tothat of Examples 2 and 3, but both lack the electric-conductionenhancing layer 42.

Referring to FIG. 10, comparison of the detecting current-appliedvoltage relationship of the gas sensor of Example 4 of the firstembodiment with that of Comparative example 1 is illustrated. The curvesof Groups (III) and (IV) respectively represent results of duplicateexperiments in which the detecting current is measured at an appliedvoltage range of 0 volt to 10 volts using Example 4 and Comparativeexample 4. The gas sensor of Example 4 has the electric-conductionenhancing layer 42 made of PEDOT, the gas detecting layer 5 made ofP3HT, and the second gaps 413 of the second electrode 41 with a width of10 micrometers (μm). The gas sensor of Comparative example 4 has astructure and a constituting composition similar to that of the Example4 except for the omission of the electric-conduction enhancing layer 42.

FIGS. 11 to 12 respectively illustrate comparison of the detectingcurrent-applied voltage relationship of the gas sensor of Examples 5 and6 of the first embodiment with that of Comparative examples 5 and 6, ina manner similar to FIG. 10. However, the results shown in FIG. 11 arefrom a single experiment. The gas sensors of Examples 5 and 6 have astructure and a constituting composition similar to that of Example 4,but the widths of the second gaps 413 of the second electrodes 41thereof are 20 μm and 80 μm, respectively. Comparative examples 5 and 6have structures and constituting compositions respectively similar tothat of Examples 5 and 6, but both lack the electric-conductionenhancing layer 42.

From the results shown in FIGS. 7 to 12, it can be seen that regardlessof the material used for making the gas detecting layer 5, the gassensors of Examples 1 to 6 correspondingly have a higher detectingcurrent with the same voltage relative to the gas sensors of ComparativeExamples 1 to 6 where the electric-conduction enhancing layer 42 isomitted. This shows that the electric-conduction enhancing layer 42 cancooperate with the second electrode 41 to increase the detectingcurrent. Furthermore, it can also be seen from the graphs thatvariations in the width of the second gaps 413 do not have a largeeffect on the results of the measurements of the detectingcurrent-applied voltage relationship, thus making the gas sensor of thedisclosure suitable for mass production.

Referring to FIGS. 13 to 18, the gas sensors of Examples 4 to 6 andComparative Examples 4 to 6 are used to perform tests for ammoniadetection at different concentrations, the detecting current beingmeasured over time. The applied voltage during the tests is 5 volts forFIGS. 13 and 14, 5 volts for FIGS. 15 and 16, and 10 volts for FIGS. 17and 18. The gas sensors of Examples 4 to 6 are respectively used in thetests of FIGS. 13, 15, and 17, and the gas sensors of ComparativeExamples 4 to 6 are respectively used in the tests of FIGS. 14, 16 and18.

From the results shown in FIGS. 13 to 18, it can be seen that theelectric-conduction enhancing layer 42 of the gas sensor of thedisclosure can cooperate with the second electrode 41 to increase thedetecting current, such that the gas sensor of the disclosure mayproduce a larger detecting current even when the applied voltage is low.

Referring to FIGS. 19 to 24, the gas sensors of Examples 1 to 3 andComparative Examples 1 to 3 are subjected to tests at different ammoniaconcentrations. The applied voltage applied during the test is 5 voltsfor FIGS. 19 and 20, 5 volts for FIGS. 21 and 22, and 10 volts for FIGS.23 and 24. The gas sensors of Examples 1 to 3 are respectively used inthe tests of FIGS. 13, 15, and 17, and the gas sensors of ComparativeExamples 1 to 3 are respectively used in the tests of FIGS. 14, 16 and18.

From the results shown in FIGS. 19 to 24, it can be seen that withdifferent widths of the second gaps 413 and at different voltages, theelectric-conduction enhancing layer 42 of the gas sensor of thedisclosure can still cooperate with the second electrode 41 to increasethe detecting current, such that the gas sensor of the disclosure mayproduce a larger detecting current even when the voltage is low.

In sum, the gas sensor of the disclosure uses the second electrode 41cooperatively with the electric-conduction enhancing layer 42 to raisethe detecting current in order to increase the sensitivity of thedetecting of the gas to be detected. Such a configuration is also easierto produce relative to the conventional gas sensor with microspheres,thus making the gas sensor of the disclosure more suitable for massproduction.

In the description above, for the purposes of explanation, numerousspecific details have been set forth in order to provide a thoroughunderstanding of the embodiments. It will be apparent, however, to oneskilled in the art, that one or more other embodiments maybe practicedwithout some of these specific details. It should also be appreciatedthat reference throughout this specification to “one embodiment,” “anembodiment,” an embodiment with an indication of an ordinal number andso forth means that a particular feature, structure, or characteristicmay be included in the practice of the disclosure. It should be furtherappreciated that in the description, various features are sometimesgrouped together in a single embodiment, figure, or description thereoffor the purpose of streamlining the disclosure and aiding in theunderstanding of various inventive aspects, and that one or morefeatures or specific details from one embodiment may be practicedtogether with one or more features or specific details from anotherembodiment, where appropriate, in the practice of the disclosure.

While the disclosure has been described in connection with what areconsidered the exemplary embodiments, it is understood that thisdisclosure is not limited to the disclosed embodiments but is intendedto cover various arrangements included within the spirit and scope ofthe broadest interpretation so as to encompass all such modificationsand equivalent arrangements.

What is claimed is:
 1. A gas sensor comprising: a first electrode; a gasdetecting layer disposed on said first electrode; an electric-conductionenhanced electrode unit being electrically connected to said firstelectrode and said gas detecting layer and including anelectric-conduction enhancing layer and a second electrode electricallyconnected to said electric-conduction enhancing layer, saidelectric-conduction enhancing layer being electrically connected to saidgas detecting layer and being made of an electrically conductive organicmaterial; and an insulating unit disposed on said first electrode forpartially separating said first electrode from said gas detecting layerand said electric-conduction enhanced electrode unit.
 2. The gas sensoras claimed in claim 1, wherein: said insulating unit includes aplurality of insulating members disposed on said first electrode, anytwo adjacent ones of said insulating members being formed with a firstgap therebetween so as to expose said first electrode from said firstgap; and said gas detecting layer and said electric-conduction enhancinglayer extend into said first gaps to be electrically connected with saidfirst electrode.
 3. The gas sensor as claimed in claim 2, wherein eachof said first gaps is surrounded by two corresponding adjacent ones ofsaid insulating members.
 4. The gas sensor as claimed in claim 2,wherein said first gaps are in spatial communication with each other toseparate said insulating members from each other.
 5. The gas sensor asclaimed in claim 2, wherein said gas detecting layer covers saidinsulating members and extends into said first gaps to cover said firstelectrode exposed therefrom, said electric-conduction enhancing layercovering said gas detecting layer.
 6. The gas sensor as claimed in claim5, wherein said second electrode of said electric-conduction enhancedelectrode unit includes a plurality of spaced-apart electrode portions,any two adjacent ones of said electrode portions being formed with asecond gap therebetween, each of said electrode portions being disposedbetween a corresponding one of said insulating members and said gasdetecting layer, each of said second gaps being in spatial communicationwith a corresponding one of said first gaps such that said gas detectinglayer and said electric-conduction enhancing layer extend into saidcorresponding first gap through said second gap.
 7. The gas sensor asclaimed in claim 6, wherein each of said second gaps has a width rangingfrom 1 micrometer to 200 micrometers.
 8. The gas sensor as claimed inclaim 5, wherein said second electrode of said electric-conductionenhanced electrode unit includes a plurality of spaced-apart electrodeportions, each of said electrode portions being disposed on saidelectric-conduction enhancing layer and oppositely corresponding inposition to a corresponding one of said insulating members.
 9. The gassensor as claimed in claim 2, wherein said electric-conduction enhancinglayer covers said insulating members and extends into said first gaps tocover said first electrode exposed therefrom, said gas detecting layercovering said electric-conduction enhancing layer.
 10. The gas sensor asclaimed in claim 9, wherein said second electrode of saidelectric-conduction enhanced electrode unit includes a plurality ofspaced-apart electrode portions, each of said electrode portions beingdisposed on said gas detecting layer oppositely of said first electrodeand in a corresponding one of said first gaps.
 11. The gas sensor asclaimed in claim 1, wherein the electrically conductive organic materialis selected from the group consisting ofpoly(3,4-ethylenedioxythiophene), polystyrene sulfonate, polypyrrole,polythiophene, polyphenylene sulfide, polyaniline, polyacetylene, poly(p-phenylene vinylene) , and combinations thereof.
 12. A gas sensor,comprising a first electrode; a gas detecting layer disposed on saidfirst electrode; an electric-conduction enhanced electrode unit beingelectrically connected to said first electrode and said gas detectinglayer and including an electric-conduction enhancing layer and a secondelectrode electrically connected to said electric-conduction enhancinglayer, said electric-conduction enhancing layer being electricallyconnected to said gas detecting layer and being made of an electricallyconductive organic material, wherein said second electrode of saidelectric-conduction enhanced electrode unit includes a plurality ofspaced-apart electrode portions formed on said gas detecting layer andinterposed between said electric-conduction enhancing layer and said gasdetecting layer, any two adjacent ones of said electrode portions beingformed with a second gap therebetween to expose said gas detecting layerfrom said second gap; and wherein said electric-conduction enhancinglayer extends into said second gaps to be in contact with said gasdetecting layer.
 13. The gas sensor as claimed in claim 12, wherein eachof said second gaps has a width ranging from 1 micrometer to 200micrometers.
 14. The gas sensor as claimed in claim 12, wherein theelectrically conductive organic material is selected from the groupconsisting of poly(3,4-ethylenedioxythiophene), polystyrene sulfonate,polypyrrole, polythiophene, polyphenylene sulfide, polyaniline,polyacetylene, poly(p-phenylene vinylene), and combinations thereof.